What causes "description is required for tool %q" in googleapis/mcp-toolbox?

Add a meaningful 'description' to the tool's config entry.

description is required for tool %q

Error message

description is required for tool %q

What it means

Identical guard to error 1182 but in cloudhealthcaregetfhirstoremetrics: Initialize rejects Config values with an empty Description. The metrics tool must describe to the LLM what store metrics it fetches, so a description is mandatory at init time.

Source

Thrown at internal/tools/cloudhealthcare/cloudhealthcaregetfhirstoremetrics/cloudhealthcaregetfhirstoremetrics.go:69

}

type Config struct {
	tools.ConfigBase `yaml:",inline"`
	Type             string                 `yaml:"type" validate:"required"`
	Source           string                 `yaml:"source" validate:"required"`
	Annotations      *tools.ToolAnnotations `yaml:"annotations,omitempty"`
}

// validate interface
var _ tools.ToolConfig = Config{}

func (cfg Config) ToolConfigType() string {
	return resourceType
}

func (cfg Config) Initialize(context.Context) (tools.Tool, error) {
	if cfg.Description == "" {
		return nil, fmt.Errorf("description is required for tool %q", cfg.Name)
	}

	params := buildParams(false)
	return Tool{
		BaseTool: tools.NewBaseTool(
			cfg,
			tools.GetAnnotationsOrDefault(cfg.Annotations, tools.NewReadOnlyAnnotations),
			tools.Manifest{Description: cfg.Description, Parameters: params.Manifest(), AuthRequired: cfg.AuthRequired},
			params,
		),
	}, nil
}

// validate interface
var _ tools.Tool = Tool{}

type Tool struct {
	tools.BaseTool[Config]

View on GitHub (pinned to 8cc6e09de2)

Solutions

Add a meaningful 'description' to the tool's config entry.
Fix YAML indentation/key spelling so Description parses.
Set Description when constructing Config in code.
Run a config validation/startup dry-run before deployment.

Example fix

// before
  get-fhir-store-metrics:
    kind: cloudhealthcare-get-fhir-store-metrics
    source: my-healthcare-source
// after
  get-fhir-store-metrics:
    kind: cloudhealthcare-get-fhir-store-metrics
    source: my-healthcare-source
    description: Gets metrics for FHIR stores in a Cloud Healthcare dataset.

Defensive patterns

Strategy: validation

Validate before calling

if strings.TrimSpace(cfg.Description) == "" {
    return errors.New("tool 'cloudhealthcare-get-fhir-store-metrics' is missing a description")
}

Type guard

func descriptionPresent(cfg Config) bool { return cfg.Description != "" }

Try / catch

tool, err := cfg.Initialize(ctx)
if err != nil && strings.Contains(err.Error(), "description is required") {
    return nil, fmt.Errorf("add description for %q in tools.yaml", cfg.Name)
}

Prevention

Never copy a tool config block without including its description
Validate required fields in CI via YAML schema checks
Set descriptions when constructing Config programmatically
Run a startup dry-run to surface init errors early

When it happens

Trigger: Initializing a cloudhealthcare-get-fhir-store-metrics tool whose Config.Description is empty — missing 'description' key in tools.yaml or unset field in programmatic config.

Common situations: Omitting description when copying another tool's config block; YAML indentation putting description outside the tool mapping; templated config generation dropping empty fields.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/5574155a180637dc. Report an issue: GitHub.